Migrate FileMaker fmscript skill

skills/filemaker-fmscript/references/fmscript-0.90.md

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+# `.fmscript` 0.90 grammar reference
+
+Source: <https://fmscript.org/spec.html>
+
+This is a concise working reference to the public 0.90 grammar overview. The
+published page is not yet the complete script-step catalogue. When a particular
+step or parameter variant is uncertain, use a known-good FileMaker/ai2fm export
+or validate it with ai2fm; do not infer syntax from another step.
+
+## Core grammar
+
+- Give a parameterized script step exactly one bracket group containing all of
+  its parameters.
+- Do not add brackets to a step with no parameters.
+- Separate main arguments inside the brackets with a semicolon followed by a
+  space. Do not use a comma as the main argument separator.
+- Use `# ` for a FileMaker comment step.
+- Continue the same multiline comment step with `#>`.
+- Use `// ` before a script step to represent a disabled step.
+- Preserve `//` and `/* */` comments that occur inside FileMaker calculations.
+- Qualify field references with their table occurrence, for example
+  `Customers::Name`. Do not emit a bare `::Name` reference.
+- Prefix a local variable with one `$` and a global variable with exactly `$$`.
+- Keep simple steps on one line.
+- Preserve multiline calculations and determine their boundary using the known
+  step name, balanced brackets, and continuation structure.
+
+## Representative forms
+
+```text
+Show All Records
+Set Field [ Customers::Name ; "Ada" ]
+Set Variable [ $name ; Value: Customers::Name ]
+Perform Script [ Specified:From list; "Normalize Customer"; Parameter: $name ]
+```
+
+```text
+# Prepare the payload
+Set Variable [ $payload ; Value: JSONSetElement (
+  "{}" ;
+  [ "id" ; Customers::ID ; JSONString ]
+) ]
+```
+
+The exact parameter labels and internal punctuation belong to the individual
+FileMaker step definition. Verify them rather than generalizing from these
+representative forms.
+
+## Review checklist
+
+- Use an exact, supported FileMaker step name.
+- Give each parameterized step one balanced outer bracket group.
+- Keep calculation parentheses and internal brackets balanced.
+- Use semicolons for main arguments.
+- Fully qualify every field reference.
+- Use `$` and `$$` variables correctly.
+- Close every structured block with the complete matching FileMaker closing
+  step.
+- Preserve comment steps, disabled steps, and calculation comments correctly.
+- Preserve multiline calculation boundaries.
+- Apply the project's formatting, naming, path, and output-only requirements.
+- Validate uncertain or version-specific syntax through ai2fm or a known-good
+  export before describing the script as round-trip ready.